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Abstract

High-contrast imaging systems with a stellar halo suppression level of 10−10 are required for direct detection of Earth-like extra-solar planets. We investigated a novel high-contrast imaging system with an unbalanced nulling interferometer (UNI) followed by phase and amplitude correction (PAC), which not only can reduce starlight but also can suppress the speckle level caused by wavefront aberrations. We successfully demonstrated that wavefront aberrations were sufficiently magnified by the UNI and the magnified aberrations were effectively corrected in amplitude and phase with two deformable mirrors. We confirmed that the suppression level of the speckle pattern with the proposed optics was beyond the limit of the adaptive optics performance.

Figures (8)

Schematic optical layout of a high-contrast imaging system consisting of a first AO, an unbalanced nulling interferometer (UNI), a second-phase amplitude correction AO, and a final-stage nulling interferometer (coronagraph).

Schematic complex amplitude distributions in each stage of the high-contrast imaging system with UNI: (a) at the collimated beam of a telescope, (b) at one arm in the UNI after phase compensation by the first AO system, (c) at the other arm after a slight reduction of the unaberrated amplitude, (d) after the unbalanced nulling, (e) after the phase and amplitude compensation by the second PAC AO, and (f) after the last nulling interferometer (coronagraph).

(Upper) Acquired images (using monochromatic 671 nm laser) of the focal plane camera (a) using the Arm 1 beam through the bright output of the 3D Sagnac interferometric coronagraph, (b) the Arm 1 beam through the nulled output of the 3D Sagnac, (c) the UNI output beam observed at the nulled output of the 3D Sagnac, and (d) after the PAC AO operation of (c). (Lower) Azimuthally averaged intensity profiles of the upper four images. The acquired images are normalized by the peak value of (a) “Arm 1 & Bright” output.

Comparison of the integrated speckle intensity through the 3D Sagnac nulling interferometer and σε2 at each stage. (a) Integrated speckle intensity within the 2.7 λ/D radius; (b) variance of the CAC modulus σε2; and (c) σε2 with the NCP effect.